Multi-office telephone system



Sept. 3, 1957 C. R. FISHER, JR

MULTI-OFFICE TELEPHONE! SYSTEM 8 Shee'ts-Sheet 1 Filed Nov. l2, 1953 m ...lm mmz ON tmhnxsx ZOcRmxql c. R. FISHER, JR 2,805,288

MULTI-OF F ICE TELEPHONE SYSTEM Filed Nov. 12.- 195s 8 sheets-sheet 2 Sept. 3, 1957 Sept. 3, 1957 c. R. FISHER, JR

MULTI-OFFICE TELEPHONE SYSTEM 8 Sheets-Sheet 3 Filed NOV. 12, 1953 Sept. 3, 1957. c. R. FISHER, .JR

MULTI-OFFICE TELEPHONE SYSTEM 8 Sheets-Sheet 4 Filed NOV. 12, 1953 Sept. 3, 1957 Ac. R. FISHER, JR

MULTI-OFFICE TELEPHONE SYSTEM s sheets-sheet 5 Filed NOV. 12, 1958 m. 0mmA Om. O

Sept. 3, 1957 c. R. FISHER, JR

MULTI-OFFICE TELEPHONE SYSTEM 8 Sheets-Sheet 6 Filed Nov. 12,- 1953 Sept. 3, 1957 c. R. FISHER, JR

MULTI-OFFICE TELEPHONE SYSTEM 8 Sheets-Sheet 7 Filed NOV. I2, 1953 Sept. 3, 1957 c. R. FISHER, JR

MULTI-OFF ICE TELEPHONE SYSTEM 8 Sheets-Sheet 8 Filed Nov. 12. 1953 United asesnss Murri-oratori *ininterrotta svsrnivi Application November 12, 1953, Serial No. 391,579

3 Claims. (Ci. 179-27) The present invention relates to multi-oiiice telephone systems in general and more particulariy to an interexchange trunk circuit for use between a main dial office `or a tandem office and a community dial oice.

ln such a system it is desirable, for economic reasons, to utilize the same trunk circuit for extending calls from either local dial equipment or a toll board over a trunk line to a distant community dial oice. trunk circuit is used for both types of calls, however, the problem of proper supervision exists since a toll operator requires ash busy supervision for the purpose of providing ya visual indication as to the progress of the call, while hash busy in the local switch train is highly undesirable.

lt is well known in the art that automatic collect and message register apparatus, associated with the local dial equipment on calls from paystations and metered lines, respectively, is operated in response to answer supervision. It is necessary, therefore, to prevent the application of ash busy to the local dial equipment so that the paystation and message register apparatus will not be falsely operated on lan incompleted call. It is also desirable to prevent the application of reverse battery clicks to the exchange subscribers receiver.

Accordingly, it is a general object of this invention to provide an interexchange trunk circuit which is accessible to either a toll board or local dial equipment in a irst exchange for extending calls to a second exchange.

It is a further object of the invention to provide a trunk circuit of the type disclosed which will return the required supervisory signals to either the toll board or the local dial equipment.

It is a more specific object of this invention to provide an interexchange trunk circuit which will repeat a steady supervisory signal to either a calling toll board or calling local dial equipment and will repeat a ashing supervisory signal only to the calling toll board.

Briey, e invention accomplishes the above cited objects by providing a two way trunl; circuit, accessible to both local dial equipment and a toll board on outgoing calls, which discriminates between steady and hashing supervisory signals returned over the trunk line from the distant office. The trunk circuit is arranged to repeat both steady answer supervision and flashing busy supervision to the toll board over the HS conductor. Answer supervision is repeated to local dial equipment by reverse battery and a timing device in the trunk circuit prevents the application of reverse battery on ash busy.

The timing device in the trunk circuit comprises a slow release relay which has a longer release time than the interval of time between succeeding ashes in the flash busy signal. If steady answer supervision is received, the relay releases to reverse battery. If flashing supervision is'received, the relay remains operated to prevent the reversal of battery.

The invention, both as to the organization and method of operation together with objects and advantages thereof, will best be understood from the following descrip- When the same tion when read in connection with the accompanying drawings.

The drawings consist of nine gures `on eight sheets and, when arranged according to Fig. 9, show the present invention.

Fig. 1 shows the trunking diagram of the described system;

Figs. 2 and 3 show a paystation adapter circuit which is connected between a line iinder and a rst selector in the local switch train of a tandem office;

Fig. 4 shows the two-way trunk circuit in a tandem oice;

Fig. 5 shows composite equipment and a part of the two-way trunk circuit in the community dial oce;

Fig. 6 shows the remainder of the trunk circuit in the community dial oftice and skeletonized drawings of an incoming selector and a connector in the community dial oiice;

Fig. 7 shows a skeletonized version yof a toll cord circuit at a toll board and an outging trunk circuit in a toll oflice;

Fig. 8 shows an incoming trunk circuit in a tandem oce.

The general operation of the system can best be understood by reference to the trunking diagram of Fig. 1,. As shown, the system comprises toll otiice A, tandem oce B, and community dial oice C. Trunk line 11 interconnects oces A and B and trunk line 4| interconnects oices B and C.

The toll board 71 in toll ofce Amay be of the type shown and described in the copending Reagan application, Serial No. 331,627, tiled january 16, 1953, and assigned to the same assignee as the present application. Calls for office B or C are extended from the toll board to outgoing trunk circuit 70 which is connected over trunk line 11 to incoming trunk circuit 80 in tandem oice B. Incoming selector S1 in ofiice B is directly associated with trunk circuit Si). Trunk circuits '70 and 80 have been shown as one-way for the purpose of simplifying the disclosure. lt is to be understood that in practice these trunk circuits would be two-way so that subscribers in oiices B and C would have access to toll 'oice 70.

The switching circuits in the tandem and community dial oices have been shown as including a at type step-by-step switch of the type sold under the trademark XY For a detailed description of this switch, reference may be had to the Frank A. Morris Patent 2,567,650, which issued September ll, 1951, and is assigned to the sameassignee as the present invention. Briey, the switch has a main set of brushes which move horizontally in a primary direction to select a level -of terminals and then move into the banks to select a particular set of terminals in the selected level. For the purpose of making Fig. 1 more compact, the switch banks have been shown below rather than to the side of the box which indicates a particular switching circuit. In a at type switch, the brushes encounter the first level of the switch bank as they move away from the switch.

Therefore the level directly beneath the box has beenV designated level 1, while the level furthest away from the box has been designated level 0.

In the tandem oiiice B, the second bank level of incoming selector S1 is shown connected to connector 32 to enable the toll operator in oiiice A tokextend calls to local subscribers in office B. The seventh level of inl coming selector 81 is shown connected by cable 3 to Y trunk circuit 4i) to enable the toll voperator in oice A to extend calls to local subscribers in omce C.

- Local subscribers in tandem oice B, such as Sta. l, can extend calls to other local subscribers in oce B through the local switch train comprising line finder 22, paystation adapter 20, first selector 31, and from the second level of first selector 31 to connector 32. Paystation adapter 20 is of the type which discriminates between calls from ordinary Vsubscribers and paystations, and -is eiectivelonly in vtheeventthatthecalloriginates at a paystation. A suitable adapter and associatedpaystationA equipmentis` shownandf described in detail in .the copending Pharis application, -Serial No. 149,072, .-led March l1, 1950, and assigned to the same assignee-aszthe present application. Y

The seventh level of iirst selector 31 is shown connectedby-cable3 toftrunk circuit l40 tofenable vsubscribers in oiice YB to extend calls to subscribers in: ofticeV4 C. vIt is to be noted thattrunkcircuit -40isaccessibletofthe toll board 71Vv throughthe banksI of.v incoming selectorSLl'and it is also accessible to subscribers of office B through-the banks offrst selector 31;

' TrunkA circuit 40 is connectedoverf'trunkline-41totrunk circuit 50 in oiceC. The third level of incomingv selector 61fin foice C, .lwhich'is directly associated with1trunk circuit 50, is shown connectcd-tolconnector 65 'which has access to local subscribers, such as Sta. 2. i, f

:Local subscribers, such as Y Sta. :2in: oice .C, lcanfextendf-calls toother local 'subscribers :in ofiiceC through the local switch train comprising line finder 63,.:'irst -selector 64 'and connector 1455. A'1.`l:re:fth'level of 'fiirst selector 64 is shown connected by cable 6 to trunk circuit .50for thepurposeof routing 'callstosubscribers in'oice B. On a'lcall-which isincoming from oice-CtoroceB, incomingpsele'ctorfll lis directlyfassoiated withitrunk circuitf 40. :The second 'level of- .incoming selector t41 .is

Y Yshown-connected-to'connector :32 which, aspreviously mentioned, has access to subscribers lines fsuch.as:Sta.;l.

inary make contacts 306 on relay 300, lower winding of relay 250, unoperated contacts 362 f relay 360, operated preliminary make contacts 307 on relay 300, conductor R2 and through the lower winding of relay 370 to battery. At contacts 301, relay 300 closes ground through resistor R33, and through the upper bias winding of reverse battery relay 250 to battery. Relay 250 does not operate'atV this time since its-windings areV diiferentially connected. Seizure of the paystation adapter and the operation of paystation-relay 300 also/closes acircuitlfor the operation of the `calling-bridge relay330fof the -paystation adapter over the following circuit: fgrourd, upper winding of relay 330, upper winding of coin detector-,relay 340, operated contacts 303 of relay 300, unoperate'd contacts 241 of relay`240,unoperated contacts 222 of relay 220, conductor T1, loop of the subscribers station, con ductor R1, unoperated contacts 224 of relay 220, unoperated contacts 243 of relay-240,operated contacts.305

Y of relay 300, the lower winding ofrelay340. and -the'lower .ever, thisfcircuit is ineective at thistime since -it'isfshunted Thedial equipment inoices B andfCiis of .thecon- VVentional` 4-wire 'v typev and' has= been shown y in lblock and fragmentary form in the Adrawings of ythis application. If'a more y completeunderstanding of VYthis equipment is desired, reference may be had to-'several kcopend-ing applications. vSelectors 31,41, S64Jand81 maybeof the type fshown and described in Vthe .copending Pharis flapplication, Serial No. 260,736, iiledDecemberS, v1951, -andf assigned tothe same assignee .as thepresenthapplication.' Connectors '32 and 65 maybe-oflthe type `dis- -closed 'in the copending .#Elliott application, J-Serial No. 271,408, yfiled February V13, .1952, fandfassigned E:to the same assignee 'as -the present application.

vInvtheY drawings anddescriptiomlthe exchange battery is shown as plus and: minusfand* describedas ground and battery. Itis to be understood thateinthissysternthe positiver terminal .of the.batteryisgroun'ded aridis, there# fore, Vreferred toas ground. .'Ihenegativeter-minallof ythe-battery is referredtofasbattery.

Av ldetailed descriptionA ofthe1 system follows.

CALLFROM 'STTIONSTA- l IN TANDEM OF FICE B TO";S"],"ATIONSTA.v 2 -IN 'COMMUNITYDIL `OFFICE`-C It will first be assumed thatstation Sta.. l is apaystation -and thatg ground is connected to Ythe"HSl'terminalassociated with llinecircuit 21v inthe banksi of lineiinder-22. Referring to Fig-2, when the subscriber 4at statio'uStaVl lifts-his receiver, line circuit 21-'andlinender-22 function in the'well known manner lto connect-thelline!circuiticonfductors Vthrough i to the i tip,ring, sleeve, `land hunt 4 conductors T1, R1, S1, and HSI, respectively, rwhich are associatedwithlpaystation adapter-20- Ground potential on'lthe HS' bank terminal inline cir'- 'cuitl21 is routed through thefline Vnder l22f1to"Y the YHSI conductor linlthepaystation adapter y20,l through=unop `era-ted contacts -234 Vof relay 236, unoperated contacts 254-of`relay'250 'and the winding of paystation' relay30tl to battery. Relay 300 operates 'in lthis circuit.

Y In 'response-tol the operation of relay300 fa'loop is closed -to Vthe' calling bridge 'relayT-370 -in irsts'elector Y31 over 'the'f following path ground, yupper winding of the 'calling' bridge relay'370, conductora-T 2, `operated'prelim- :by normal tor closed contacts 362-'on'relay 360. Ground returned from first selector 31 over conductor f S2 -is `-connected through unoperated contacts 363 'on relay 360, -unoperatedy contacts 236 on relay'230, to conductorsl forthe A4purposeof holding operated theline tinder'and .the line circuit cut-olf relay in' awell known manner.

When the callingpaystationsubscriber deposits acoin, -theloopcircuit-is unbalanced, .as shown'andldescribed, for1example,inrthe copending Pharis application, Serial No. 149,072, and serves'fto'operate diierential coinde- -tector relay 340. VSleeve relay 350 nowoperatesfrorn ground on conductorSZ, through' operated ycontacts '341 -on.relay 340, 'operated-'contacts 324 on relay'320, and its #winding tobattery. `Relay 350, nat its operated contacts 2353 and 354,"s'nunts the upper-and lower windings, re-

spectively, offrelay340 to effectively removez'it from' the circuit'andcause itstrelease. Relay 350 1ocks 'itself op- Yerated .through its nowoperated contacts 358 to ground on conductor? S2. Dial tone'returned from'the iirst selector 31, over conductors T2 and R2, is` connected=through -condensers C32-and'C33 and through"operatedzcontacts #355' and 356 'onrelay `350to`conductors T1 and vR1, respectively. `Operation of sleeve relay'l also-closes an. obvious circuit' fronrground` through its operated` contacts 359 and through the windingfof sleeve `delay-relay z361Mo battery. v Y

*.Relay :360v operates inv this circuit and Yopens .contacts f362 to remove the shunt from the'impulsingcontacts'331 onr'relay3'30. Also, relay 360.subs`titutes a localy ground Vat operated transfer 'contacts 364 fory thejground on. conductor `S2through break contacts -363for connectionzto conductorSl.

:'The. connectionv of dial. tone Ito lthe tipsand ring con- -ductors T1 `and Rl, respectively, informs the ipaystation subscriber lthatfihe 4may '-now dial the desired ffnumber.

In responsetothe dialvimpulsearcalling `bridge-relay i330 lpuls'es the` 'previously described Aloop to f `relay 370, :iin:first'selector-BLat conta'ctsl.V 'Uponthe iirstre- 'leaseA offrela'y B30 ':infresponse -toithe iirst dial pulse, -shunt relay310 operates over a circuitfextending from lground through unoperated .contacts 1333v of @relay 330, operatedcontacts'323 of relay 320, operated-.contacts 308 of relay 300, and the winding-or" relayftl tobattery'.

At-:operated Acontacts 311, Vrelayla@ connects resistor R32Yin parallel-'with the 4lower #windinggof -relaylZStl :to 'improve the qualityof impulses Vdelivered to lthe calling @,sougss bridge relay of first selector 31. If it be assumed that the rst digit dialed is 7, the impulses of the rst digit cause a suitable switch in selector 31 to step to the seventh level. The selector then searches for an idle trunk in that level and switches through in any suitable manner to seize trunk circuit 40.

The previously described loop closed by paystation adapter 29 to conductors T2 and R2, is connected to conductors T3 and R3 when the selector 31 switches through. Calling bridge relay 430 in trunk circuit 40 now operates over a circuit extending from ground through the upper winding of relay 430, through unoperated contacts 471 of relay 476, over the A3 conductor to composite equipment 51, the upper left winding of repeat coil RC51, unoperated contacts 461 on relay 400, over the T3 conductor, through the previously described loop in paystation adapter 2t), conductor R3, unoperated contacts 403 on relay 400, the lower left winding of repeat coil RC51 in composite equipment 51, conductor B3, unoperated contacts 472 of relay 478, and through the lower winding of relay 430 to battery.

In response to the operation of relay 430, battery through resistance lamp L41 is connected through Operated contacts 431 on relay 436, unoperated contacts 481 on relay 48() to the M3 lead to composite equipment 51, through the upper winding of polar duplex relay 500, through the retard coil RTS over conductor R4 of the composited trunk line, retard coil RT52, the upper winding of polar duplex relay 560, the M5 conductor, unoperated contacts 511 on relay 510, and unoperated contacts 534 on relay 530 to ground. Relay 560 operates in this circuit but relay 590 remains unoperated because of the opposing connection of its windings.

The operation of polar duplex relay 560 in composite equipment 52 serves to connect ground to conductor E5 associated with trunk circuit S0, and through unoperated contacts 544 on relay 546 to operate the pulse-in relay 559 in trunk circuit 58.

Returning now to the operation of trunk circuit 40, the operation of relay 430 also closed an obvious operating circuit for release delay relay 440 through operated contacts 433 of relay 430. At contacts 443, relay 446 disconnects the pulse-in relay 45d from conductor E3 and, at operated contacts 444, connects the winding of first supervisory relay 42) to the E3 conductor. Also at operated contacts 446, relay 44% connects ground to conductor S3 to hold operated the switch through relay (not shown) in first selector 31 in a conventional manner.

in trunk circuit 56, the operation of relay 556 serves to operate the switch relay 520, through operated contacts 552 of relay 551). A loop is now closed to the* calling bridge relay 669 in incoming selector circuit 61 in a circuit extending from ground, upper winding of relay 66d, conductor T7, operated contacts 527 on relay 520, conductor T5, upper right winding of the repeat coil RC52 in the composite equipment 52, conductor A5, operated contacts 522 on relay 520, resistor R53, operated contacts 524 on relay 520, conductor BS, lower right winding of repeat coil RC52 in composite equipment 52, conductor R5, operated contacts 528 on relay 526, `operated contacts 553 on relay 556, conductor R7, and the lower winding of relay 660 to battery. At contacts 526 relay 520 connects ground to conductor S6 to mark trunk circuit Sii as busy in the banks of first selector 64.

The dialing of the second digit in the directory nurnber now pulses relay 330 in paystation adapter 20 which, at contacts 331, interrupts the loop to relay 430 in trunk circuit 40. Relay 436 repeats the impulses of the digit at its contacts 431 to pulse polar duplex relay 560 in composite equipment 52 which, in turn, alternately connects and disconnects, in accordance with the dial impulses, ground to conductor E5 at its contacts 561 to pulse relay 550 in trunk circuit Si). Relay 550, at contacts 553, repeats the impulses to the calling bridge relay 669 in incoming selector 61. It might be well to mention at this time that a shunt relay is provided in each trunk circuit to shunt out impedance elements during impulsing to improve the pulsing ratio. As previously described, relay 310 operates in paystation adapter 20 during impulsing. In trunk circuit 40, shunt relay 460 operates from ground through unoperated contacts 434 0n relay 430, operated contacts 445 on relay 440, and through its winding to battery. At its operated contacts 461, relay 460 shunts out the upper left winding of repeat coil RC51 during pulsing. In trunk circuit 50, shunt relay 690 operates from ground on unoperated contacts 551 ofrelay 556, through operated contacts 525 of relay 520, and through its winding to battery. Relay 600, at its operated contacts 601, shorts out the upper right winding of the repeat coil RCSZ in composite equipment 52 during impulsing.

if it be assumed that the second digit dialed is 3, the impulses of the second digit cause a suitable switch in selector 61 to step to the third level. The selector then searches in that level until an idle connector, such as 65, is found. When incoming selector 61 switches through, the loop on conductors T7 and R7 is closed to the calling bridge relay 630 of connector 65, which operates.

The third, fourth, and fth digits of the directory number dialed by the paystation subscriber serve to pulse relays 330, 436, 560, 550, and 630. The connector is thus stepped in its tens and units selecting motions and the ringing switch is stepped to a position corresponding to the'ringing frequency or code of the called party. When the called party answers in response to the ringing signal, answer bridge relay 624) operates over the line in the well known manner. At contacts 621, 622, 623 and 624, relay 620 reverses battery to trunk circuit 56. However, this reverse battery signal has no eiect on trunk circuit 50. Battery through resistor R65, through operated contacts 625 of relay 620, is connected to conductor HSS, over cable 8, through incoming selector 61, over conductor HS7 to operate HS supervisory relay 510. Battery through resistance lamp L51 and through operated contacts 512 of relay 510 is now connected to the M5 lead of composite equipment 52, through the upper winding of relay 560, retard coil RTSZ, conductor R4 of the composited trunk line, the upper winding of relay 566, conductor M3, unoperated contacts 481 on relay 434, operated contacts 431 on relay 430, and lamp L41 to battery. Relay 50G) operates in this circuit and connects ground through its operated contacts 561 to the E3 conductor, through operated contacts 444 on relay 44@ to operate first supervisory relay 420.

Relay 426 operates and connects battery through resistor R44, operated contacts 424 on relay 42), conductor HSS, over cable 3 to the first selector 31, through selector 31 to the HSZ conductor, through operated contacts 365 of relay 360, to the unoperated contacts 255 of relay 256. It can be seen that this battery is ineffective to operate supervisory relay 246 in paystation adapter 20 until reverse battery relay 256 operates.

Returning to trunk circuit 4i?, the operation of relay 425) closes ground through its preliminary make contacts 423 and through its still unoperated contacts 422 to charge condenser C41 and operate the second supervisory relay 416. The combination of relay 410 and condenser C41 constitutes a timing device which is used to determine whether the signal received from trunk circuit 50 is a steady or a flashing supervisory signal. The complete operation of relay 420 connects ground through its preliminary make contacts 423 and through its now operated contacts 421 to an open contact 411 on relay 410. If relay 420 remains operated for a period of time which is greater than the discharge time of capacitor C41 in series with resistor R41 and the inductive winding of relay 410, relay 410 will release. When relay 410 releases with relay 420 still operated, the circuit is closedY .I7 tcl-.op.erat.e.Y the ithird .supervisory relay 40.0. Relay ...4.00, at. contactsAQL. 402, ..403 and 4505, reverses lthe. battery oyerconductors and R3 .which results in the opera ationpf .reverse battery relay '250 in .paystationadapter 20.... Relay -tl.closes a;locking circuitthrough its vupper windingrfrom groundcn 4operated contacts 3.6.6-.Qn relay. tlandaits Loperated Acontacts .251. The.previouslydes1-ibe l.circuitV onfconductor. H82 .is now closed through operatedpontacts*255..on relay-250 to.. operate supervisory relay 240. At4 contacts 241, 1242, 2.43 .and 244, .relay 240` re-.reverses .batteryover conductors. T1 and R1 to tllepaystation apparatus. '.-Operationof-.relay 250,4.at contacts Y254,;releases, relay 3130.A VAt contacts 302, 303, -`304 and :305, .relay .30.0, .disconnects `the bridge. relay 330, .whiohjreleasea andfmetallicallylconneots conductors T1 and R1 to conductors T2 and R2, respectively. At contacts'32, relay 330 opens thelcircuitto relay 329 whichv noweleases. :I'hecircuitsarenow in condition for .conversationrbetween the. calling. :and called parties.

4When the..calling party .replaces receiver at .the termination of Jthe conversation, .relay .43.0, .which was beingrheld .over ythe callingY loop, .is released. At .contacts '432, vrelay .430 shifts .the Mflead fromresistance battery to ground to release the polar duplex relay 560 Vincomposite. equipment 5,2.which`,` in turn, releases pulsein.rel ay.550-.in trunk circuit .55). lelaySSl), at.contacts 553, releases calling bridge lrelay 63:1)A in ,connector 65. Relay-620, .in connector..65,..releases to removebattery from the HSS conductor. Relay 510 Lin trunk circuit 50 releases and, .in turn, connects f ground to .the M5 leadto-release.polar.duplex relay 500in composite equipmentV @51. Removal Yof ground ,from conductor E3 by. thereleaselof-polar-duplex.relay 5th) releases vrelay 420 in tru-nk circuit 4t) which, `in turn, releases Arelay 400. The-release lofrrelay 420 in trunk circuit40 also .shifts thefconductor 1715.3.frorn resistance batterylto resistance ground` `to release relay 249- in .payst-ation Ladapter V20. In-tnunkcircuit50 slow `release relay 44.0 vfinally releases toA removeJg-round'at contacts 446 from conductors S3 and S27. Y

' In response to therernoval of groundA from Athe sleeve conductor S2, relay )l in paystation adapter 20 4releases. A@Ground Ythroughoperated contacts 36l of relay 360-.is now-conducted through Aunoperated contacts 352 of -relay 350. and through the winding of vcoin control relay 23010 battery. Relay v230 operates and, Vat contacts-231,. closes an. alternate vhold .circuit for .relay 250. Also, d0 I; P. M. ground is .now/connected through-inter-runterV contacts 261, operated contacts 235V of .relay 230,;u'noperated contacts. 228.y of relay 220, the Ylower winding ofV coin control l relay 220 to battery. .Ground is also connected-through operated contacts 233 of relay 23-and-the upper.windingofrelay 220 to battery. Since relay22tLis differentially connected Yit Willanot operate until ground is removedV from the V601. P. M. contacts 261; insuresrthat coinpctential will not be routed to the paystation .equipment for aperiod of ltime vless than aafull 60 I. P. M. pulse.

When interrupter contacts -26l open, .relay 220-operates over" its upperwinding. The next closure of contacts 26llroutes ground-through operated contacts 235 of relay 2Stl; operated contacts V22f7'of relay V2270, and the winding of' coin relay V'ittito battery. Relay 210 opcrates in this circuit. -i-llt)V volts is now connected through operated contacts 252 of reverse battery/relay 259, Vngrerated contacts 226 of relay 22), the Winding of cof vsupervisory relay Ztitl, operated contacts 212 of relay 2li); andgthroughoperated contacts 221 Vand223 of relay 2,26 tothe Tl and Rl cmornluctors in parallel tofcollect thecoinatthe paystationina well known manner. Re-

Ztltl' holdsqoperated in series with the coin magnet at thepaystation and at ncontacts v20,3. serves to maintainv relay 230`operated. When `thecoin is collected andtheiiaystatlsm magnet .removedfrom the lint/relay -200 feleases and opens the locking circuit vfor 'relay 230 which- 8 then releases. 4Release ofrelayrz .releases relaysZZ 2.1.0, and reverse battery relay .250.

All ,trunks .busy

Ifall connectors,such as connector 65,in 'the third level of incoming selector 61 Aare busy and incoming selector61 Vhunts't'o royerow at the completion of the second digit, 120 1. P. battery' is connected :through interrupter 'contacts-l 652, operated overliow contaetsgSl to the H57 conductor. VTl'iisbajttery ashes the HS- supervisory relay 5 10 at l120 I., P. 'M. and relay -510 flashes the'MS lead between resistancev battery and ground. V,In response to the jdashbusy returned over the` trunk line, thpolar'duplex relay 50i) is dashed at 120jI..P. M. and serves to `conlnectjand disconnect groundgto the E3 con# ductor at contacts 561; The vfirst impulse of the flashing supervisory signaloperates relay A420. Relay 420 Vcloses ground through its preliminary Vrnakecontacts 423 and through its, still vunoperated` contacts 422 to the timing device comprising condenser C41 in parallel with relay 410. This ground charges condenser C41 and operates relay 4,710. The discharge time of .the condenser C41 in seriesfwith resistor R541V and the winding of relay .410 is great enough to Ymaintain relay 416 operated during the ashnsofrely .-42.0- 11 .can .be Seen .thateach relay 420releases and reoperates tit recharges'condenser' CfljlV and reenergizes Yrelay .410 so Athat relay 410 will remain operated jfor Fthe duration of the `flashing ysupervision. 'Since relay 410v remains operated, relay 400 can-V notnoperate to reversebatterysince its circuit is held open by operated Ycontafts 411 on relay 4'10. When ,the call.Y ing party releases in response tothe Vbusy tone, which vis rellIQQd kover vthe Ytip and .ring conductors lfrom selector 6,1, thejloopis opened to relay 330- whieh releases. At contactsjll, relaytl opens .theloop to succeeding circuits toinitiate theprelease of same. Relay'320 releases when relay 330 releases.V When ground is removed from QOnduCtQrS. as previously deseribeirelavo releases, relax/.2.30 operates. .relay Sreleases. Operativa vf relay 230 opens the circuitl to paystation relay 300 atvconi tacts 23,4. Relay300 releases but performs no function at this time. As previously described, relays 220 and 210 operate. Since reverse battery supervision was not received and relay 2,59 is not operated, volts is connected through operated contacts 225 of relay 220, unoperated contacts 2,53 of reverse battery relay 250, operated contacts 226 ,of .relay 220, the winding of relay 200, operated contacts. 212 of relay l210, and through operated contacts2v21and 223 on relay A221i to conductors Tlpand R1 in paralllelV torefund the coin in the well known manner. Y

Line busy If the called line is -found busy, the busy test relay 640 in connectorv65 operates inthe well known `manner and connects -60 I. P. M. battery through interrupter contacts 653, operated contacts 641 of Arelay 640, `unoperated contacts 626 of relay '620,' to the HSS conductor. Relays 51.0, 500, 420 Hash at 60 I. P. M. in the same manner as described forthe all trunks busy condition. Relay 410 ,remains operated aspreviouslydescribed over this ashing supervision and prevents relay 400 from reversing .battery ,over conductors T3 and'R3 so that the coin will be automatically refunded when the calling party hangs up. Y

If sta-tion Sta. l is not a p aystation, paystation adapter 2 t1ris inelfectiye and Vserves merely to connect the c on. ductors T1 and (R1, to conductors T2 and R2, respectively, through normal'Y contacts fof relays 220, 240 and 300. Conductor, S1 is connected. to conductors S2 through unoperated contacts Aof relays 230 21,151,360, Trunk circuit` 40 and succeeding equipment function exactly .as previously. described. to .extend Ythe .call vto .staf tion-:Sta 2in-office C..

lha-

asoma@ CALI. FROM TOLL BOARD 71 IN OFFICE A TO STATION STA. 2 IN COMMUNITY DIAL OFFICE C The operator at toll board 71 initiates a call by inserting plug P71 into jack 171. Sleeve relay 700 operates from ground through its upper high resistance winding over the sleeve jack conductor S10, the sleeve of the calling cord, and through the supervisory lamp L71 to battery. Sleeve assist relay 710 operates from ground through operated contacts 701 on relay 700. Supervisory lamp L71 is now illuminated from ground on unoperated contacts 751 on relay 750, operated contacts 713 on relay 710, the low resistance winding of relay 700, and through the lamp to battery.

Battery, through resistance lamp L72 and through normal contacts 742 of relay 740, or unoperated contacts 733 of relay 730, is now connected through operated contacts 711 of relay 710, conductor M10, upper winding of relay 760, retard coil RT71, conductor R11 of the composited trunk line, retard coil RT81, upper winding of relay 840, conductor M12, and unoperated contacts 822 on relay 820 to ground. Polar duplex relay 840 operates in this circuit and serves to place ground on the E12 conductor to operate pulse relay S00 in trunk circuit 80. Release delay relay 810 operates from ground through operated contacts S03 on relay 800.

The loop to the calling bridge relay in incoming selector 81 is closed by the operation o f the pulse relay 800 in the following manner: conductor T12, through the upper right winding of repeat coil RCSZ associated with composite equipment 82, back over the A12 conductor, through resistor R83, over the B12 conductor, through the lower right winding of repeat coil RCSZ, back over R12 conductor and through operated contacts S01 on relay S to the R13 conductor.

When the operator throws the dial key (not shown), associated with toll board 71, battery is placed on the T conductor and ground on the R10 conductor, as disclosed in the above-identified Reagan application. The battery on conductor T10, through the upper left winding of repeat coil RC72 in composite equipment 72 and over conductor A10, operates ott-normal relay 730. Ground on the R10 conductor, through the lower left winding of repeat coil RC72, conductor B10, and through operated contacts 732 on relay 730, operates the pulse relay 720. Ground through operated contacts 731 on relay 730 and through operated contacts 721 on relay 720 operates oft-normal l relay 740 which locks through its operated contacts 741 independently of contacts 721. It is to be noted that operation of these relays insures that a false pulse will not be sent over the M lead while the circuit is being prepared for pulsing. Contacts 722 close an alternate path for the resistance lamp battery before contacts 742 open.

The ground on the ring R10 lead is interrupted by the dial springs of the operators dial (not shown) and pulse relay 720 follows these impulses. M10 lead battery is pulsed at contacts 722 of relay 720 to pulse the polar duplex relay 840 in composite equipment S2. Relay S40 repeats the impulses over conductor E12, at contacts S41, to relay 800 and relay 800 repeats the impulses to succeeding circuits at its contacts 801. In trunk circuit S0, relay 830 operates on the rst release of relay 800, during impulsing, from ground through unoperated contacts 802 on relay 800 and operated contacts 811 on relay 810. Relay 830 remains operated over the impulses of a digit and at operated contacts S31 shunts the upper right winding of repeat coil RC82. Since this call is to be routed to subscriber Sta. 2 in oice C, the operator will dial the digit 7 and the incoming selector 81 will be stepped to level seven and hunt in that level to seize an idle trunk circuit such as trunk circuit 40.

The loop closed by operated contacts 801 on relay 800 is now connected through incoming selector 81 to seize calling bridge relay 430 in trunk circuit 40. As previ- 10 ously described, the operation of relay 430 serves to operate relay 440 and also to connect battery through lamp L41 to the M3 lead to seize relays 550 and 520 in trunk circuit 50. Relay 520 closes the loop to incoming selector 61, as previously described.

Further digits dialed by the operator are now repeated by relay 720 in trunk circuit 70, the polar duplex relay 840 in composite equipment 82, relay 800 in trunk circuit 80, relay 430 in trunk circuit 40, polar duplex relay 560 in composite equipment 52, relay 550 in trunk circuit 50 and the calling bridge relay in either the incoming selector 61 or the calling bridge relay 630 in connector 65. w

If an all trunks busy condition is encountered by incoming selector 61, I. P. M. battery is connected to the HS7 lead, as previously described, to flash the HS supervisory relay 510. Relay 510 ashes the M5 lead in accordance with the flashing supervisory signal to alternately operate and release polar duplex relay 500 which, in turn, repeats the ashing supervision to the rst supervisory relay 420. Relay 420 repeats the flashing to the HSS conductor by alternately connecting battery through resistor R44 and its operated contacts 424 and ground through resistor R45 and its unoperated contacts 425. This flashing battery and ground on conductor HSS is connected over cable 3 through incoming selector 81 to the H813 lead to flash supervisory relay 820 in trunk circuit 80. Relay 820 connects battery through resistance lamp L81 and through its operated contacts S21 and over the M12 conductor to ash the polar duplex relay 760 in composite equipment 72 which, in turn, flashes the E10 conductor to alternately operate and release supervisory relay 750 in trunk circuit 70. Ground through unoperated contacts 751, operated contacts 713 on relay 710, and through the low resistance winding of the relay 700 and over the sleeve 10 conductor illuminates supervisory lamp L71. Lamp L71 will not light in series with the high resistance winding of sleeve relay 700 but it is illuminated from ground through the low resistance winding. Thus, the ilashing of contacts 751 on relay 750 will alternately illuminate and extinguish supervisory lamp L71.

1f a line busy condition should be encountered in connector 65, relay 640 in the connector serves to connect 60 I. P. M. battery to the HSS lead, as previously described. This ashing is repeated by relays 510, 500, 420, 820, 760 and 750 to ash the operators supervisory lamp L71 at 60 I. P. M.

When the operator restores her dial key at the completion of dialing, battery is removed from tip conductor T10 and ground is removed from ring conductor R10. Relays 730, 720 and 740 in trunk circuit 70 release.

If the called line is idle, the connector switches through to seize line circuit 62 and to ring the ringer at substation Sta. 2. When the called party answers in response to the ringing signal, answer bridge relay 620 operates, as previously described. Relay 620 connects battery through resistor R65 and through its operated contacts 625 to the HSS conductor. This steady supervisory signal operates relay 510 in trunk circuit 50 which repeats the steady supervisory signal to relays 500, S20 and 750. The operation of relay 750 serves to open contacts 751 so that the operator is given steady dark supervision by supervisory lamp L71.

When the operator wishes to release the connection at the termination of the conversation, she withdraws plug P71 from jack 171 to release relay 700. Relay 710 releases and connects the M10 lead to ground through its now unoperated contacts 712. The polar duplex relay 840 releases to remove ground from conductor E12 and thus release relay 800 in trunk circuit 80. Relay 800, at contacts 801, opens the loop to trunk circuit 40 to release trunk circuit 40 and the succeeding circuits, as previously described.

11 einen non. AroLrw no ,s ,anni .onmennfro isrArroN; sra.A u1:, 1N ormone Y'Ilzunlrl K QrsmitsY iand' ,filnjction *in .the ,same manner 4aslpreviously described to seize incoming selector V81. Dialing of the digit 12i`nto theinccmins. .Selector 81 'causs the `ilicouing Selector 't0 seize ,connector 3.2. urther digits dialed' into connector32 'serveto direct the connector lto seize and rring the calledj linefin the'well known marmer- CALL Enola;s.rrrr,1 cn-1isla,L incarica C ro sranonsr-Antm ormone Y 4Removal of the receiver by the subscriber Sta.Y 12' in otic'eJC servesftoconnecbthe station line conductors to therfstselectori' in a/welleknown manner; UT he subscriberthen dials the digit55into-selector 64and selector 64 'hunts'in leveliive and switches throughfto'idle trunk cireuit'-50; -Calling'bridge'relay-530vin trunk circuit 50 operates oyerithe'lfollowingpathf: groundethrough its upper winding, -unoperated Vcontacts 52`-1on relay *520, the A5 conductoryupperqght winding of -Yrepeat coil RC5-2, conductor T5, unoperated contacts 61.1 onv relay' 610, conductorT, through the -subscribers subset, back Vover conductor-R6, unope'rated contacts 613 onrelay 610, -conductorV R5, lower right 'winding *ofV 4repeat coil" R652, conductor' B5, unoperated contacts 52.3 on relayv 520 Y and through itsV lower resistance winding Ytol'battery.

Release delayrelay-Sfit) operates from groundV through contactsr531 of relay 530. Battery, through resistance lamp'LSl-,voperated .contacts 533-ofrelay530, vunoperated contacts 511l of relay 510, is'connected to the Mlead to operate the polarduplex relay 500m composite-equipment 51.V Relay 540, upon operation, connects ground through contacts-'542 tosleeve conductorV S6'Y -to hold operated the preceding circuits. Operationof relay 500 closes ground through its contacts 501' -to the E3 lead and through upoperated contacts 443 on relay 449 to operatethe-pulse-in relay 450 initrunlr circuit 40. Switching-relayf470 operates'fr'om ground on oper-atedr contacts- 452'ofrelay 450. A loop is now closed to the incoming selector 41` overa circuit extending from conductor T9, operated contacts 477 of relay 470, through the-upperleft Ywinding of repeatcoil R051, conductorA A3, -operated contacts 471A on relay1470, resistor R43, operated contacts y473 on relay 470, conductor B3,V the lower left Windingv of Vrepeat coil RCSII, operatedV contacts 478 of relay 470, Voperated-contacts 453 ofrelay 450toconductor R9. This loop circuit seizes the ivcallingrbridge relay vin the incoming selector 41` and ground returned from inc'omingrselector41 lover the S9lleadfa'nd thrmlghoperatedV contacts 479 of Vrelay 47d energiz'esrthe lower hold winding of the switching relay 470.'

Dial impulses are repeated bycalling bridgerelay 536, polar duplex relay 500 and pulse-in relay450. Relay 450 repeats thel impulses to the incoming selector 41 at its contacts 453. Succeeding digits which are utilized to direct the operation of connector 32 are repeated in `the same manner.

When the called party at Sta. v1 answers in response to a ringing signal, connector 32 serves to connect resistance battery to conductor HS9 of trunk circuit 40 to operate the fourth supervisory relay 480. Relay 480 connects battery through resistance lamp L41 and through its operated contacts 482 to the M3 conductor to operate relay 560 yin composite equipment52. Relay 560, at contacts' 561, connects ground to the E5 conductor and through operatedcontacts-543 of relay 544? to operate the supervisory relay 6719 in trunk circuit 50. Relay 61'0, at contacts 61,1, 612, 613 and' .614, reversesv battery over conductors T6 and R6 to the Yprecedingequipment.

When the calling party; restores Vhis receiver, the llcop is opened to caliingbridge relay'530 which releases.` Re` l'fyl S30-removes battery from ther M5 conductorY to re lease polar duplex relay 500 and pulse-in relay/:459.:4

12 'Relay 450 opens'the loop to connector 32-at contacts 453. When connector A32V releases, ground iseremoved from conductor vS9 to release .relay4 47,0,and resistance battery is removed fromconductor H89 to release v V1-Velay 48,0. Release .of relay 480 lswitches the M3 conduetor to ground to releasethepolar duplex relay 576i) which, in turn, removesrground from the E5 conductorA to release vrelay 6,10. Slow release relay l540 inftrunlr circuit 50 releases to .renioyeiground from conductor S6 andthereby, release the preceding circuits. 1 Y

It is believed apparent fromtheabove description that a trunkcircuit has been provided whichcang be utilized to route calls from either a local switch train or from a `toll train overatrunk vlineto a distantoce.Vv Y It ,should also be apparent that this trunk circuit provides Ythe proper supervision to either Vthe local switch train or ,to-the toll train. i t While there has .been described what is vat presentgon-` sidered to be thepreferred embodiment of theinvention, itwill be understoodthat various modifications may be made therein and it is intendedto cover in the appended claims all suchmodications as falljwithin the true and scope of the invention.

Whatis claimed is: l

l. Ina telephone system having rst `and seconde);- changes `interconne'ctedby a;trunk line,.a trunk circuit in said Yiirst exchange terminating said trunk line, means in said 'rstexchange for extending a connection toV said trunk circuit, s'aid connection including line conductors, means in said trunk circuitfor extending the connectionl over sadtrunkline to` said second'exchange, means in said second exchange for returning a steady supervisory signal overthe trunk line to the trunk circuit, v*means in saidsecond exchange for returninga flashing supervisory signal over thetrunk line to the trunk circuit, and means in said'trunk circuit responsiveonly to saidsteady Supervisory signal 'for reversing battery over said line conductors.

V2. In a telephone system havingtirst and secondex; changes interconnected'by aV trunk line, a trunk circuit in said rst exchange terminating said trunk line, means in said iirst exchange. for extending a vconnection to said trunk circuit, said connection including*V line conductors, means in said'trunk circuit for extending the connection over said trunk line to saidsecond exchange,v

means in said second exchange for returning a steady, supervisoryv signal' over the trunk line to the trunk circuit, means in Said second` exchange for returning la,V flashing supervisory signal over the trunk Yline to thetrunk circuit, means Vin said'trunk circuit operative in response to said steady supervisorytsignal to reverse battery oversaid line conductors and operative in` response to said flashing supervisory signal to Vprevent the reversal of battery over said line conductors.

3. In a telephone system having rlrst and second exchanges interconnected'by a trunk line, a trunk circuit in` said iirstexchange terminating saidtrunk line, means :in said first exchange for extending Va connection toV said trunk circuit, said connection including line-conductors and a control conductor, means in said trunk circuitfor extending the connectionA over saidv trunk linel to said second exchange, means in said second exchangeV for returning a steady supervisory signal over the tnmkline t`o the trunk circuit, means in said second exchangefon returning a flashing supervisory signal over theV trunk line to the trunk circuit, means in said trunkircuit responsive: to said steady supervisory signal for repeating said steady supervisory signal over said line conductors t and saidY control conductonand |responsive to said flashingsupervisory signal f or. repeating saidflashing supervisory signal over only said control' conductor.`

4. vIn a telephone system having f rst andmsecondrex changes interconnectedby a; trunkV iine, a trunk circuit in.

saidV iirst exchange terminating saidtrunl line, means Ain said frst exchange for extending -a connection yto said' trunk circuit, said connection including line conductors and a control conductor, means in said trunk circuit for extending the connection over said trunk line to said second exchange, means in said second exchange for returning a steady supervisory signal over the trunk line to the trunk circuit, means in said second exchange for returning a flashing supervisory signal over the trunk line to the trunk circuit, a source of potential, means in said trunk circuit operative in response to said steady supervisory signal for reversing battery over said line conductors and for connecting said source of potential to said control conductor, and operative in response to said ashing supervisory signal to prevent the reversal of battery over said line conductors and for connecting said supervisory potential to said control conductor.

5. In a telephone system having first and second exchanges interconnected by a trunk line, a trunk circuit in said first exchange terminating said trunk line, means in said rst exchange for extending a connection to said trunk circuit, said connection including line conductors, means in said trunk circuit for extending the connection over said trunk line to said second exchange, means in said second exchange for returning a steady supervisory signal over the trunk line to the trunk circuit, means in said second exchange for returning a flashing supervisor] signal comprising pulses over the trunk line to the trunk circuit, tirst means in said trunk circuit operated continuously in response to said steady supervisory signal and operated and released in accordance with the pulses of said flashing supervisory signal, timing means in said trunk circuit having an operating time greater than the interval of time between succeeding pulses of the ilashing supervisory signal, means for initiating a timing operation of said timing means in response to a first operation of the first means, means for arresting and resetting the timing operation of the timing device each time the iirst means is released and reoperated, and means responsive to the completion of the timing operation of the timing means for reversing battery over said line conductors.

6. In a telephone system having rst and second exchanges interconnected by a trunk line, a trunk circuit in said iirst exchange terminating said trunk line, means in said first exchange for extending a connection to said trunk circuit, said connection including line conductors and a control conductor, means in said trunk circuit for extending the connection over said trunk line to said second exchange, means in said second exchange for returning a steady supervisory signal over the trunk line to the trunk circuit, means in said second exchange for returning a dashing supervisory signal comprising pulses over the trunk line to the trunk circuit, first means in said trunk circuit operated continuously in response to said steady supervisory signal and operated and released in accordance with the pulses of said asln'ng supervisory signal, a source of potential, means responsive to each operation of said irst means for connecting said source of potential to said control conductor, timing means in said trunk circuit having an operating time greater than the interval of time between succeeding pulses of the ashing supervisory signal, means for initiating a timing operation of said timing means in response to a first operation of the rst means, means for arresting and resetting the timing operation of the timing device each time the iirst means is released and reoperated, and means responsive to the completion of the timing operation of the timing means for reversing battery over said line conductors.

7. In a telephone system having rst and second exchanges intenconnected by a trunk line, a trunk circuit in said rst exchange terminating said trunk line, means in said iirst exchange for extending a connection to said trunk circuit, said connection including line conductors, means in said trunk circuit for extending the connection over said trunk line to said second exchange, means in .said second exchange for returning a steady supervisory signal over the trunk line to the trunk circuit, means in said second exchange for returning a dashing supervisory signal comprising pulses over the trunk line to the trunk circuit, a iirst relay in said trunk circuit operated continuously in response to said steady supervisory signal and operated and released in accordance with the pulses of said liashing supervisory signal, a second relay in said trunk circuit having a release time greater than the interval of time between succeeding pulses ot' the ashing supervisory signal, means responsive to a first operation of the rst relay for operating said second relay, means for reenergizing the second relay each time the first relay is released and reoperated, a third relay, means responsive to the release of the second relay for operating said third relay, and means responsive to the operation of said third relay for reversing battery `over said line conductor.

8. In a telephone system having iirst and second exchanges interconnected by a trunk line, a trunk circuit in said iirst exchange terminating said trunk line, means in said first exchange for extending a connection to said trunk circuit, said connection including line conductors and a control conductor, means in said trunk circuit for extending the connection over said trunk line to said second exchange, means in said second exchange for returning a steady supervisory signal over the trunk line to the trunk circuit, means in said second exchange for returning a flashing supervisory signal comprising pulses over the trunk line to the trunk circuit, a iirst relay in said trunk circuit operated lcontinuously in response to said steady supervisory signal and operated and released in accordance with the pulses of said flashing supervisory signal, a source of potential, mea-ns responsive to each operation of said first relay for ,connecting said source of potential to said control conductor, a second relay in said trunk circuit having a release time greater than the interval of time between succeeding pulses of the dashing supervisory signal, means responsive to a first operation of the first relay for operating said second relay, means for reenergizing the second relay each time the rst relay is released and reoperated, a third relay, means responsive to the release of the second relay for operating said third relay, and means responsive to the operation of said third relay for reversing battery over said line conductors.

References Cited in the le of this patent UNITED STATES PATENTS 1,889,564 Ostline et al Nov. 29, 1932 2,021,291 Clark et al. Nov. 19, 1935 2,621,258 Balzer Dec. 9, 1952 2,669,606 Kessler et al. Feb. 16, 1954 2,745,903 Kessler May 15, 1956 

